Conventionally, skin patches (for example, plasters) for applying on skin have been extensively used. The adhesion (pressure-sensitive adhesion) of the skin patches to the skin is important because it allows drugs to be transdermally absorbed through application to the skin.
Thus, the adhesion of skin patches has been extensively studied. Attempts to use a styrene-isoprene-styrene block copolymer (hereinafter, may be also referred to as “SIS block copolymer”) as an adhesive component has been made in light of the possibility of production by heat fusion without using a solvent.
For example, a skin patch including indometacin, an SIS block copolymer, liquid paraffin and polyethylene glycol in the adhesive layer (see, Patent Document 1), a skin patch including an SIS block copolymer, crotamiton, and an anti-inflammatory analgesic drug (see, Patent Document 2), and the like have been disclosed.
These skin patches can be produced by heat fusion without using a solvent because an SIS block copolymer was included in the adhesive layer, thus enabling easy and inexpensive production, and a reduced environmental burden can be realized.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2001-302502    Patent Document 2: Japanese Unexamined Patent Application, Publication No. H4-321624